The present invention relates to a multilayer thin film structure and a process for manufacturing the structure and mounting it on an electronic packaging substrate.
In general, a multilayer thin film structure is fabricated directly onto an electrically-good substrate such as a ceramic or glass-ceramic substrate. Such a fabrication process has several drawbacks including cost, work in progress concerns because of the serial nature of the manufacturing sequence, and undesirable processing/handling of highly-valued ceramic and glass-ceramic substrates. Further, if the fabricated multilayer thin film structure is defective, then an otherwise electrically-good substrate must be discarded or reworked, at considerable cost.
Various processing schemes have been proposed which allow for multilayer thin film structures to be fabricated separately from the electronic packaging substrate on which they will ultimately be employed. The following are examples of such processing schemes.
Perfecto et al. U.S. Pat. No. 5,534,466, the disclosure of which is incorporated by reference herein, disclose a method of making a multilayer thin film structure on a temporary glass carrier which then can be transferred to a substrate for permanent joining. In this method, the multilayer thin film structure is made in a “top down” format which becomes righted when it is permanently joined to the substrate. It is noted that the top metal ground plane is formed either flush with the surface, as shown in FIG. 9, or is recessed as shown in FIG. 15. Both of these embodiments present certain difficulties during testing. Further, the multilayer thin film structure is joined directly to the substrate which requires that the substrate be extremely planar to accommodate the rigid multilayer thin film structure.
Arjavalingam et al U.S. Pat. No. 5,534,094, the disclosure of which is incorporated by reference herein, discloses the manufacture of a multilayer thin film structure on a quartz carrier. Also included is a polymeric separation layer between the multilayer thin film structure and the quartz carrier which can be laser ablated so that the multilayer thin film structure can be easily separated from the quartz carrier in a later stage of manufacturing.
Prasad et al. U.S. Pat. No. 6,281,452, the disclosure of which is incorporated by reference herein, discloses a compliant polymeric spacer which joins and electrically connects the multilayer thin film structure to the substrate. The spacer as disclosed has a number of advantages including strain relief.
Gorczyca et al. U.S. Pat. No. 5,161,093, Noddin et al. U.S. Pat. No. 5,276,955, Traskos et al. U.S. Pat. No. 5,329,695 and Saia et al. U.S. Pat. No. 5,699,234, the disclosures of which are incorporated by reference herein, disclose other multilayer packaging schemes, some of which are also applicable to multilayer thin film structures.
It is a purpose of the present invention to have a thin film transfer join process and multilevel thin film module in which the chip joining pads are readily available for testing.
It is another purpose of the present invention to have a thin film transfer join process and multilevel thin film module in which the chip joining pads enhance the chip joining yield.
It is yet another purpose of the present invention to have a thin film transfer join process and multilevel thin film module in which limited processing must occur after the multilevel thin film structure is joined to the substrate.
These and other purposes will become more apparent after referring to the following description of the invention considered in conjunction with the accompanying drawings.